Hi everyone.
I'm currently working in Hg2+ determinations vía dithizone complex formation. I prepare several dilutions from 400 ppm to 5 ppm to make a calibration curve so I can measure complex at 488 nm.
The problem is: visually, reactions show differences but on spectrophotometer some absorbance values increase at certain concentrations while others decrease and there is no apparent pattern so I can make a linear calibration curve.
Has anyone worked in this type of determinations at that range of HgCl2 concentration? Any help you could give me would be unvaluable.
Thanks!!
Dithizone spectrophotometric won't help you since it is SO insensitive. The maximum concentration in potable water is 0.020 ppb (?). Thus the 'cold vapor' method was developed.
Actually maximum concentration is 2 ppb but I work with the higher concentrations mentioned because I'm involved in a mining wastewaters project and ICP or CV-AAS isn't always possible on field.
What is the method recommended for mining wastewater by the EPA? What is the limit? You may be able to use the CV-AAS method if the interference are complexed (for example citric acid or EDTA) beforehand.
As I recall Sodium Borohydride reactant can be consumed by other compounds.
Not familiar with your current approach but judging from the picture you included something is precipitating starting at 80 ppm. That would one of the limiting factors for the method. Cold Vapor AAS is ideal. I used it for a few years. Matrix effects do limit it. Organic sludges cause problems.
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